A standard wind turbine generator has a nacelle that is installed in a manner that allows yawing on top of a pillar like tower, which is erected upright on the ground or is installed offshore, and wind turbine blades are supported on a rotor head that is supported so as to be rotatable about a shaft on the front side of this nacelle, thereby constituting a wind turbine rotor blade. The respective wind turbine blades receive wind force to rotate the rotor head, and this rotation is speeded-up through a gear box to drive a generator, which is installed inside the nacelle, thereby generating electricity. The nacelle is slew drive controlled such that the rotation center axis of the rotor head (wind turbine rotor blade) always points in the upwind direction to achieve efficient, generation of electricity. The nacelle houses, in addition to the generator, heat generating devices of various types, such as an inverter, a transformer, and so forth. In order to maintain stable operation of the wind turbine generator, these electrical devices need to be properly cooled.
As disclosed in Patent Literature (hereinafter, referred to as “PTL”) 1, for example, an internal cooling structure of a nacelle of a conventional wind turbine generator achieves cooling of the heat generating devices by providing an electric ventilation fan inside the nacelle to forcedly introduce the outside cold air into the nacelle. In addition, as disclosed in PTL 2, there is a wind turbine generator in which the heat generating devices installed in a nacelle are encapsulated, thereby making a closed-loop air duct for delivering cooling air into the capsule with a fan; a cooler is provided on the downwind side of the wind turbine blades along this closed-loop air duct to enable air-cooling of the cooler with the outside air, thereby achieving heat exchange with the cooling air flowing inside the cooler.
As disclosed in PTLs 3 and 4, there are wind turbine generators that are provided with an outside-air intake for taking in the outside wind on the front of a rotor head to allow cooling of internal devices in the rotor head with the outside air from this intake; however, all of these wind turbine generators merely take in the outside air into the rotor head, and none of them perform cooling of the interior of the nacelle.